Porcelain and ceramic formulations to protect metal from heat and corrosion, and to provide electrical insulation have been around since the early 1900's. This form of protection was and is used in the so-called ‘white goods’ industry (stoves, refrigerators, ovens, tubs, sinks, etc.). The earliest known usages of such coatings were on ancient Egyptian jewelry.
Previous applications of these glass- and/or clay-based protective coverings have ranged from use in the previously mentioned white goods industry to certain chemical storage containers to certain types of food processing and/or cooking containers. One of the problems that occurs when applying these coverings is that there are small pin hole exposures and crevasses in the hard outer shell that allow permeation (penetration) of the outer shell by the outside influences of such corrosive elements as gases, moisture and alkaline or acidic liquids. This permeation problem particularly follows exposure of the metal substrate to any significant degree of thermal shock, which tends to expand any fractures or surface imperfections in the outer shell and to further expose the underlying metal substrate, thereby speeding corrosion processes. Corrosion, of course, adversely affects the metal substrate, weakening it, and can result in complete failure of the covered metal parts.
Some industries have tried to use certain bare metal alloys and coated metal alloy substrates to overcome harsh oxidation and corrosion problems. The problem with most metal alloys (and certainly with exotic metal alloys) is cost and the persistent problem of short-term life expectancy of the metal part under many operational conditions, regardless of the nature of the conventional coating used. (Steel companies may claim that use of their alloys extends the life expectancy of a part when exposed to heat, even up to 1200° F. However, such alloys (which cannot be acid-resistant) so-exposed are now particularly subject to corrosion under even normal operating conditions.)
Examples of the above mentioned problems and shortcomings abound. For instance, the oil drilling and extraction industry uses expensive alloys and hardened carbon steel pipes and parts in the field. But even these pipes and parts have very short life expectancies due to the particularly abrasive and sometimes corrosive effects of the pumped-in gases and slurries as well as the corrosive effects of the heat and acids which form naturally in the wells.
Oil and gas refineries have a similar problem, particularly with sulfuric acid corrosion. Remarkably, for the normal repair of corroded and weakened parts, the entire refinery is typically shut down for as much as thirty days or more.
The mining industry has similar problems with the wear and related parts used in mining processes. Caustic or acidic chemicals and/or abrasive particulate slurries are regularly used in this industry. All of these environs are quite destructive to the coatings and to the metal substrates themselves. Silicon-based epoxies and industrial coatings are currently used to protect these metal substrates, but these coatings are subject to very rapid wear and degradation. Thus, the metals must be re-coated frequently.
These problems and challenges also exist in pulp and paper manufacturing, electric power generation, etc.
In many industries and applications, ultraviolet (UV) rays also have a damaging effect on traditional protective coatings, causing them to deteriorate even more quickly.
Even in industries where harsh environments are not the norm corrosion can present major problems. For example, galvanized steel structures, sheets and parts are used extensively in agriculture such as in pipes, grain storage silos and other containments, livestock food and water troughs and conveyances, etc. Corrosion is a problem for two reasons—despite galvanizing. First, galvanizing offers better protection of the steel than paint or other industrial coatings, but it is still an essentially temporary zinc coating over the metal substrate that it is intended to protect. But second, and more importantly, as the galvanized coating corrodes, zinc—a known toxic heavy metal—leaches into animal foods and water supplies, into grains and other consumer foods and into the ground, groundwater and water supplies.
In the same way, as galvanized steel guardrails degrade and corrode, they also leach toxic zinc into the ground, groundwater and water supplies.
In recognition of these problems with zinc plating and/or galvanizing, many jurisdictions in the United States and Europe (Europe has banned zinc effective 2007) are actively considering serious restrictions or bans on the use of zinc. Certain jurisdictions already have enacted such serious restrictions or even outright bans on the use of zinc.
Some helpful prior art methods and systems for metal cladding are described in U.S. Pat. No. 6,518,209 B2 issued Feb. 11, 2003;U.S. Pat. No. 6,800,375 B1 issued Oct. 5, 2004 and U.S. Pat. No. 6,818,314 B1 issued Nov. 16, 2004 to Gary Wilson, all entitled CHEMICAL RESISTANT GLASS FUSING COMPOSITION AND PROCESS FOR METAL MOTOR VEHICLE AND BUILDING INDUSTRY ARTICLES. These patents focus on using a dry mix of frit and frit additives (e.g. boric acid, potassium hydroxide, dry-sodium silicates and optionally pigmentation for color) to fuse compounds to metal articles for better chemical, thermal, electrical and corrosion resistance.
Even in view of the above Wilson patent contributions, many of the problems described above persist and their solutions have remained elusive.